<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <!-- 最新版本的 Bootstrap 核心 CSS 文件 -->
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

<!-- jQuery (Bootstrap 的所有 JavaScript 插件都依赖 jQuery，所以必须放在前边) -->
<script src="https://cdn.jsdelivr.net/npm/jquery@1.12.4/dist/jquery.min.js"></script>
<!-- 最新的 Bootstrap 核心 JavaScript 文件 -->
<script src="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
<style>
    @media screen and (max-width: 768px) {
        .c1 {
            color: red;
        }
    }
    @media screen and (min-width: 768px) {
        .c1 {
            color: green;
        }
    }
    @media screen and (min-width: 992px) {
        .c1 {
            color: blue;
        }
    }
    @media screen and (min-width: 1200px) {
        .c1 {
            color: yellow
        }
    }
</style>
</head>
<body>
    <div class="container">
        <h1>hello world</h1>
        <ul>
            <li>hello1</li>
            <li>hello1</li>
        </ul>
        <hr />
    </div>
    <div class="container-fluid">
        <h1>hello world</h1>
        <ul>
            <li>hello1</li>
            <li>hello1</li>
        </ul>
        <hr />
    </div>
    <div class="c1">
        hello world
    </div>
    <div class="container">
        <div class="row">
            <div class="col-xs-12 col-sm-6 col-md-4 col-lg-3">a1</div>
            <div class="col-xs-12 col-sm-6 col-md-4 col-lg-3">a2</div>
            <div class="col-xs-12 col-sm-6 col-md-4 col-lg-3">a3</div>
            <div class="col-xs-12 col-sm-6 col-md-4 col-lg-3">a4</div>
        </div>
        <hr />
        <div class="row">
            <div class="col-xs-6">a1</div>
            <div  class="col-xs-6">a2</div>
            <div  class="col-xs-6">a3</div>
            <div  class="col-xs-6">a4</div>
        </div>
    </div>
</body>
</html>